1. Field of the Invention
This invention relates to an image forming apparatus such as electrophotographic apparatus, ink-jet printers, etc. of a type, which effects image formation on a recording material such as paper, etc. with the use of developer, ink, and the like.
2. Description of the Prior Art
An image forming apparatus such as, for example, an intelligent copier, using a laser beam printer operates in such a way that it receives image information in the form of electrical signals, scans the surface of a photosensitive drum with use of a laser beam flashing in accordance with the electrical signals to thereby form an electrostatic latent image, then a developing agent (toner) stored in a developer container is caused to adhere onto the electrostatic latent image to render it viewable, and the thus developed image is transferred onto a recording member such as plain paper. The toner remaining on the surface of the photosensitive drum without being transferred is scraped off with a cleaner. Since this toner has a lowered developing performance, and, moreover, contains therein paper dust, it cannot be re-used, hence the toner is collected in a collecting vessel as disabled toner (or refuse).
In the above-described construction of the image forming apparatus, the quantity of the toner in the developer vessel decreases as the recording operations are repeatedly conducted, while the quantity of the disabled toner in the collecting vessel increases. When the toner in the developer vessel begin to run out, the transferred image on the recording sheet becomes thin or uneven. On the other hand, the disabled toner can fill up the collecting vessel and stain the interior of the image forming apparatus.
Accordingly, when the toner begins to run out in the developer vessel or toner refuse fills up the collecting vessel, there has generally been taken a step to detect the toner shortage in the developer vessel and/or the fill-up of the toner refuse in the collecting vessel to stop operations of the image forming apparatus, or to display the result of the detection. Specifically, when the toner shortage in the developer vessel and/or the fill-up of the toner refuse in the collecting vessel is detected, any of the following actions has been taken:
(1) The detected result is displayed but the image forming operations are continued;
(2) Image forming operations are stopped after discharge of the printed sheet currently being processed; or
(3) Image forming operations are stopped with discharge of the last printed sheet in a continuous printing operation.
With the above action (1), when an operator gives no attention to the display of the detected result and continues the printing operation to the end, the reproduced images become thin and the toner refuse fills up and overflows from the collecting vessel with the result that the warning display is of no use at all.
With the above actions (2) and (3), a down-time occurs in the image forming apparatus in spite of the toner remaining in the developer vessel to an extent that enables the apparatus to continue its normal operations, which requires intervention by an operator.
The above-described various inconveniences take place not only with the toner used in a laser beam printer, but also with toners used in ordinary reproduction apparatuses and ink, and the like used in ink-jet printers.